Other Parts Discussed in Thread: LM53602-Q1, LM43602, LM53603
Hello,
I'd like to ask some questions about LM43602-Q1.
- At the input voltage of 6 to 6.5 V that will not rise further, will a LM43602-Q1 switch its switching mode between PWM/CCM and PWM/DCM or between PWM/DCM and PFM/DCM automatically depending on the load condition unlike LM53602-Q1?
- LM53602-Q1 will be forced to operate in PWM unless its input voltage once goes above its threshold of about 6.8 V.
- Is the timing of switching mode changes (CCM to/from DCM in PWM and PWM to/from PFM in DCM) determined by the input voltage? I guess from the data sheet that it depends solely on the inductor current. I'd like just to confirm.
- What will the LM43602-Q1's minimum drop-out voltage look like? If the idea is the same as LM53602-Q1, I guess the high-side MOSFET's RON is a major factor. Could you provide me with the possible Max RON of the LM43602-Q1's high-side MOSFET? It's not written on the data sheet.
- In theory, the minimum input voltage that hits the tOFF-MIN restriction is estimated at 5.71 V when the VOUT is 5 V. However, Figure 12 of the data sheet shows the switching frequency starts to drop at around VIN = 6.0 V with IOUT = 1.5 A. What's wrong with my estimation?
- The duty cycle when it hits the tOFF-MIN with FS = 500 kHz is 87.5% (= (2 µs - 250 ns (tOFF-MIN (Max)))/(2 µs) × 100%).
- VIN under this condition is estimated at 5.714 V from the equation D = VOUT/VIN, here VIN = VOUT/D = (5 V)/(0.875).
- What are the recommended external component values for the following operating conditions?
- FS = 500 kHz, VIN = 5.5 to 14.5 V, VOUT = 5 V, IOUT = 0 to 1.5 A
- If they are on the 10th column of Table 2 of the data sheet (FS = 500 kHz, VOUT = 5 V), can the COUT be smaller than the recommended 100 µF? Which performance will be degraded if the COUT is smaller than 100 µF?
Best regards,
Shinichi Yokota